Web control means and method for bag making machine

ABSTRACT

An apparatus and method for making and filling bags from plastic film, wrapping an endless supply about a forming and filling tube where the supply has a plastic zipper profile extending intermediate the edges of the film material, controlling the feed of film over a sharp edge of a former so that a tension free slack is maintained in the film to eliminate the possibility of distortion or damage to the small rib and groove interlocking zipper profiles on the film.

BACKGROUND OF THE INVENTION

The present invention relates to improvements in form, fill and sealmachines, and more particularly to a bag forming machine wherein anendless supply of plastic film with a zipper intermediate the edges isfed over a forming and filling tube and the edges sealed to form atubular bag.

In a form, fill and seal operation, an endless continuous supply of filmis brought forwardly and is shaped and wrapped around a filling andforming tube. The shaped film has its edges brought together and joinedto form a tubular container. Contents are dropped through the fillingtube into the container and cross-seals are formed to provide lengths ofbags which are cut apart. In one method of forming bags in a form, filloperation, the film is provided with reclosable rib and groove zipperprofiles extending longitudinally along the film parallel to the formingaxis of the film. In the formation of the film into tubular form, theprofiles can be joined as the bag is formed. It has been discovered thata stable operation can be accomplished by utilizing film where theprofiles are already joined and are located intermediate the edges ofthe film. In this operation, the edges of the film are brought togetherto form a bottom seam for the bag. An example of a bag formation wherethe profiles are brought together is shown in Tilman U.S. Pat. No.4,355,494. In U.S. Pat. No. 4,617,683, to Christoff and Ausnit, theformation of bags is illustrated where the raw edges of the film arejoined, and in the present arrangement, a formation procedure such asthat shown in the Christoff et al patent is employed with film beingsupplied where the interlocked profiles are located intermediate theedges of the film.

The packaging of products for retail sale and consumption has developedgradually over the years in order to enhance the ease with which theconsumer can open the packaging in order to gain access thereto for useor consumption of the food product therein. In the form, fill and sealoperation described above, such reclosable packages can be developed atrelatively high manufacturing speed using an endless supply of filmwhere the profiles are already extruded as part of the film andpreviously interlocked. In such packaging and package making, thecontainers are manufactured with the interlocking rib and grooveprofiles accurately and critically made so that they will protect thecontents, such as foodstuffs, therein and yet be readily opened andreclosed. The profiles are made to be very relatively minute, and assuch with accurate manufacturing tolerances, the shape and size of theprofile must be accurately maintained and not distorted either inmanufacture or in storage. It is a desirable attribute of such packagingthat the bags be closed securely in an airtight manner to maintainfreshness of a food product remaining within the package. The foodproducts may be of varying types such as that which are packaged andstored within a box or carton which has the bag as an internal liner orpouch to contain dry cereal products. Other forms of packages or pouchescan be made which are handled, stored and sold without a protectivecarton surrounding them.

The success of this type of packaging, which affords the customer with areopenable package, relates to having mating flexible closure stripswhich interlock and do not afford leakage. Also, the flexible closurestrips must be capable of being handled and reclosed easily. The successof such closures depends to a great extent upon avoiding deformities inthe profiles while the material is being handled and particularly whileit is being fed forwardly onto the forming machine and being completedby having the bottom seam and side seams formed.

In the formation of these pouches, the film is fed forwardly atproduction manufacturing speeds over the forming and filling tube.Acceptable manufacturing procedures require that the film be advancedintermittently with the advance stopped while the bottom seam andcross-seams are being formed. After the seams are formed, the film mustagain be accelerated so that a new pouch can be made after the previousone has been formed and filled. Such film advances must be accomplishedwithout unnecessarily stressing and unnecessarily distorting theinterlocked profiles. It has been found that distortion can easily occurwhile the film is drawn around curves or bends in the formation.

One location where distortion has occurred is in the location where thefilm is shaped over forming shoulders while being fed onto the formingtube. With the interlocked profiles located between the edges of thefilm, it is necessary to draw the film over relatively sharp formingedges. If the profiles are drawn with tension over such forming edges,the longitudinal tensions caused lateral forces on the film which tendto open the groove of the interlocked film. The groove is formed withside legs and a sharp pull on the film will tend to spread the legs ofthe groove to cause a distortion in the size and shape of the groove.This causes an insecure interlock and an insecure holding of the rib sothat the rib and groove loses its efficiency and effectiveness.

FEATURES OF THE INVENTION

An object of the present invention is to provide an improved form, filland seal machine capable of continuously forming pouches or bags whereinthe size and shape relationship of the rib and groove remain intact andthe opportunities for the profiles to be damaged or distorted aresubstantially eliminated.

A still further object of the invention is to provide an improvedforming machine for forming bags from a continuous supply of film havinginterlocked profiles thereon wherein damage caused by pulling the filmin tension over edges in the mechanism are eliminated.

A still further object of the invention is to provide an arrangementwherein bags are made from a film having interlocked profiles thereonand a method and structure is provided for maintaining relaxing slack inthe film particularly at the location of the profiles during the timewhen the film is drawn forwardly over forming surfaces and edges.

A further object of the invention is to provide an arrangement forfeeding film to a vertical forming machine wherein the film has fastenerprofiles therein and the film can be fed with the fastener profilesoffset from the center of the film without causing problems in feedingand bag forming such as by resultant skewing of the film. An object isto allow feeding film over a vertical forming machine wherein thevertical seam to be joined can be on the back side of the forming tubeor offset from the center of the forming tube.

In accordance with the features of the invention, an endless supply ofthin plastic film is supplied in sheet form with interlocked profilesintermediate the edges. The film material is fed up an inclined rampover a relatively sharp bending or folding and shaping edge. A film feedis provided which maintains a tension preventing slack in the film sothat the profiles are not pulled taut over the bending edge which shapesand forms the film. The film guiding control which maintains the slackis driven off the apparatus which advances the film over the formingtube. The structure is arranged so that the slack which is generated isprevented from becoming too great to disturb the formation and causewrinkling in the film by slippage in the feed when the slack becomes toogreat.

Other advantages, features and objectives will become more clear withthe teaching of the principles of the invention in connection with thedisclosure of the preferred embodiments in the specification, claims anddrawings, in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a forming and filling machineconstructed and operating in accordance with the principles of thepresent invention;

FIG. 2 is an enlarged sectional view taken substantially along lineII--II of FIG. 4;

FIG. 3 is a side elevational view of the forming mechanism of FIG. 1also illustrating the arrangement for feeding film to the machine;

FIG. 4 is a fragmentary elevational view in somewhat schematic formshowing a portion of the film feeding apparatus;

FIG. 5 is an enlarged vertical sectional view taken through the axis ofthe forming arrangement and generally showing a portion of the structureof FIG. 4;

FIG. 6 is a fragmentary enlarged sectional view taken substantiallyalong line VI--VI of FIG. 5; and

FIG. 7 is a fragmentary side elevational view shown in schematic form ofanother form of the invention for providing web slack in the feed; and

FIG. 8 is a fragmentary side elevational view shown in schematic form ofanother embodiment of the invention for producing slack in the web feedto the critical location to prevent damage to the zipper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a continuous length of film 10 fed forwardly anddownwardly over a forming tube 11. The forming tube is hollow and openat the top so that contents can be dropped therethrough into the tubularpouch which is formed from the film.

Film is drawn incrementally forwardly by suitable means such as drivebelts 12 and 13 which engage the surface of the film at opposite sidesof the forming tube 11. As an alternative, the film may be pulleddownwardly by cross-seaming devices 14 and 15 which move together toclamp the film and form a seam 16 which seam forms a side seam on thebag. The film has rib and groove interlocked profiles on the sideopposite the bottom seam 9 in the film. The bottom seam is formed by aseaming device 17 which heat seals the film edges 10a and 10b together.The belts for drawing the film incrementally downwardly over the tube 10are driven by suitable mechanism 18 which is activated incrementally asthe film is to be advanced by timing means for the machine.

FIG. 3 illustrates the supply of thin plastic film for the machine. Asupply of film is carried on a roll 31 with the film having beenpreviously formed by extrusion with shaped interlocked profiles 10c,FIG. 2, between the film edges 10a and 10b. A guide roll 24, which willbe described in greater detail later, carries the film just prior to itbeing received by the forming and filling machine, and the roll 24 has agroove 24a accommodating the additional bulk 10c of the profiles. Theremainder of the film 10 rides on the surface of the roll 24 whichcontrols the speed at which it is fed into the machine and the roll 24is such that primarily it pushes the film to maintain non-tension slackin the film prior to it being fed over forming shoulders 34. If theslack becomes too great, the film slips on the surface of the guide andspeed control roll 24.

Returning the FIG. 3, the supply of film material is initially indoubled form with the profiles 10c at the edge. As the film is unwoundfrom the roll 31, it is spread out in single layer form by spreaders 30.The film then passes upwardly over a guide roll 29 to be fed onto supplyrolls 25 and 39. 39 maintains a wrap of the film over the roll 25.

The film then passes over a supply and guide roll 41 which maintains awrap of the film over the roll 24. As the film travels down over theguide roll 24, it ascends up a ramp 33 shown in greater detail in FIG.5.

After the film ascends the ramp 33, the film edges 10a and 10b areshaped over curved shaping shoulders 34 which guide the edges onto theforming tube 11 to cause the film to wrap the tube. The film edges 10aand 10b then are drawn together to form the seam 9.

In the center of the film, the interlocked rib and groove profiles 10care turned downwardly at the top of the ramp 33 over an upper edge 36 ofthe ramp. The profiles of the film then pass downwardly between theouter surface of the tube 11 and a vertical guide plate 40 which is partof the ramp assembly. The profiles are loosely held between the tube 11and the vertical plate 40 as illustrated in FIG. 6.

In order to shape the film and form the tube, the film must be turnedover an edge, such as shown at 36, causing a sharp turn 37 in the filmat the location of the profiles. As the film is pulled downwardly by thebelts 12 and 13, normally this will create a severe tension at thelocation of the profile 10c causing the legs of the groove profile tospread and tending to damage the critical tolerance between the rib andgroove of the interlocked profiles.

To avoid this sharp pull on the profiles which would be caused at theturn edge 36, a tension free slack 35 is formed in the web at the rampwhich is located in a preshaping portion 35 of the web which is inadvance of the forming shoulders 34. To maintain this tension free slack35, the guide roll 24 drives the film so that the slack is maintained.An additional support roll 32 is located at the lead edge of the ramp toaid in stabilizing the film as it slides up the ramp.

To maintain the slack 35, a slack portion is first included in the filmwhen the machine is loaded. In this manner if the guide roll 24 isdriven at the speed of web advance, the slack will be retained. However,in one preferred form, the guide roll 24 is driven at a speed onlyslightly greater than the speed at which the film is pulled down overthe forming tube 11.

The guide roll 24 is driven incrementally at the same time as when thebelts 12 and 13 advance the web.

As shown in FIG. 3, the guide roll 24 is driven off of the same drive 18as drives the belts, and a shaft 19 is driven by the drive 18 andcarries a chain sprocket 20 thereon. The chain sprocket drives chain 21which drives a sprocket 22 which in turn drives the guide roll 24. Anidler roll 28 maintains the chain 21 under the proper tension. Thesprocket 22 is a double sprocket driving a chain 23 which drives asprocket 26 driving the supply roll 25. An idler tension roll 27maintains the chain 23 at the proper tension. The supply roll 41 isdriven at the same speed as the film advance belts 12 and 13 are driven.The guide roll 24, however, is arranged to be driven at a surface speedonly slightly in excess of that of the surface speed of the pull downbelts 12 and 13 and the supply roll 25.

As illustrated in FIG. 5, the roller 38 positioned above the shoulder36, and the vertical guide strip 40 allow for uneven lengths of film tobe pulled over the shoulder 36 without falling off to one side orwithout skewing. This allows a bag to be made wherein the seam at theedges of the film can be formed at one side of the forming tube 11. Inother words, the film can be supplied with unequal widths of film ateach side of the zipper. This allows the zipper to be located at anydesired location on the face of the finished bag and the location of thezipper is not limited to being exactly at the top of the bag when theseam which joined the edges of the film is at the bottom. The fact thatthe machine must feed profile film requires more than just the shoulder36 to turn the film. The vertical guide plate 40 is necessary to providethe vertical guiding surfaces for the film and profile.

Still referring to FIG. 5, the slack shown at 35 in the film allows thefilm to be more easily guided by the profiled zipper.

FIG. 7 illustrates an alternate arrangement for controlling feed of thefilm. In FIG. 7, a layer of film is fed forwardly with a zipper integralin the film supply 45. The film web is pulled forwardly by a pinchroller drive including rollers 46 and 47. A bubble chute 48 ispositioned at the base of an inclined ramp 50. A proximity switch 49 islocated in the depth of the U-shaped bubble chute. The bubble chuteallows for accumulation of the film web to insure web slack and zerofriction at the forming shoulder and collar which are located at the topof the ramp. The proximity switch 49 controls the pinch roller drive andsignals the web drive to increase or reduce the acceleration of thepinch roll drive for the film. Devices heretofore used have provided anaccumulator or dancer arm located on the dispenser upstream from the webrollers. These prior devices do not minimize the friction at theshoulder collar to eliminate zipper damage and eventual malfunction ofthe zipper closure.

FIG. 8 illustrates another form of controlling the feed of a film webhaving a zipper profile therein. The film web 51 is fed forwardly andpasses over a booster roller 52 which is movable laterally to controlthe size of a bubble 54 in the web. The position of the booster roll 52is controlled by a reciprocating cylinder 53. The cylinder acts as abooster to pull a bag length of film from a dispenser supply roll duringthe rest cycle of the machine. The accumulated film forms the bubble 54which provides minimum tension and friction when pulled over theshoulder during the bag feed cycle. The arrangement should includezipper guides in the roller 52. This arrangement eliminates the need forpower dispensers and upstream zipper guides. It also eliminates zipperdamage and zipper closure problems which occur if feeds of designstructures heretofore available are used which provide severe bendingand tension in the zipper passing over the forming shoulders. A pawl 56is located at the base of the ramp 55. In operation during the time abag is being filled and seamed, the booster roller 52 is moved to theleft by the cylinder 53 to form the bubble loop 54. The roller 52 isthen pulled back to the solid line position shown in FIG. 8. When afresh length of web is pulled downwardly over the forming tube, the webis pulled against the slack formed by the bubble 54. The unidirectionalpawl 56 prevents tension on the web when the booster roller 52 is movingto the left from the solid line to the dotted line position of FIG. 8.

In operation, this maintains the tension free slack 35. As this slackgrows slightly, the film 10 will slip slightly on the roll 24. As soonas the slack at 35 tends to diminish, the film begins to tightenslightly around the guide roll 24 so that it maintains the slack 35.Thus, the roll 24 constitutes a feeding means for the film whichcontinually operates to maintain a tension free slack at the preshapingportion of the web in advance of the forming tube 11. The ramp is apreferred arrangement for feeding the web to the forming shoulders 34,but it will be understood that the film can approach the formingshoulders at different angles. Regardless of the approach arrangement, atension will occur causing the profiles to be bent over an edge or asurface. Not only will the profiles be bent, but an axial pull will beexerted to pull the profiles over an edge which has to be located at theentry to the forming shoulders.

In operation, axial stress and bending stress, both of which tend todistort the profiles, are avoided by maintaining the slack in advance ofthe forming shoulders.

Thus, it will be seen that I have provided an improved bag formingarrangement capable of making bags continuously from thin lightweightfilm which has critically shaped and sized interlocking profilesthereon. The arrangement meets the objectives and advantages set forthabove and is capable of operating under circumstances of high speedproduction for continuous forming of bags and pouches from plastic film.

I CLAIM AS MY INVENTION:
 1. A form, fill and seal machine for makingreclosable zipper bags, comprising in combination:means supplying anendless sheet of film with interlocked rib and groove profilesintermediate side edges of the film; a forming and filling tube overwhich the sheet of plastic film is shaped for joining edges of the filmto form a tubular container; forming shoulders for guiding the endlesssheet of film onto the tube bringing the film edges together; and meansfeeding the film from the supplying means to said shoulders forming atension free slack preshaping portion in the sheet in advance of saidshoulders preventing profile distorting forces on the profile.
 2. Aform, fill and seal machine for making reclosable zipper bagsconstructed in accordance with claim 1:and including an inclined rampleading to said forming shoulders for supporting the tension free slackportion.
 3. A form, fill and seal machine for making reclosable zipperbags constructed in accordance with claim 1:including guide meanssandwiching the profile portion as it passes onto the forming andfilling tube.
 4. A form, fill and seal machine for making reclosablezipper bags constructed in accordance with claim 1:wherein said feedingmeans is a roll wrapped by the film.
 5. A form, fill and seal machinefor making reclosable zipper bags constructed in accordance with claim4:including a supply roll positioned ahead of the feeding roll tomaintain a wrap over the feeding roll.
 6. A form, fill and seal machinefor making reclosable zipper bags constructed in accordance with claim4:including means for advancing the film over the tube; and meansconnecting said advancing means drive to said roll for driving the rollat a greater speed than that which the film is advanced over the formingand filling tube.
 7. A form, fill and seal machine for making reclosablezipper bags constructed in accordance with claim 1:including a shoulderpositioned between the feeding means and the tube over which theprofiles are bent when the film passes onto the tube.
 8. A form, filland seal machine for making reclosable zipper bags constructed inaccordance with claim 1:wherein said film feeding means drives the filmat a speed faster than the film is advanced over the forming and fillingtube to maintain said tension free slack.
 9. A form, fill and sealmachine for making reclosable zipper bags constructed in accordance withclaim 1:wherein said film feeding means is a feeding roll over which thefilm is wrapped; and wherein slippage occurs between the film andfeeding roll when said tension free slack reaches a predeterminedexcessive amount.
 10. A form, fill and seal machine for makingreclosable zipper bags, comprising in combination:a forming and fillingtube over which a continuous web of plastic film having interlockingprofiles is shaped for joining edges of the film to form a tubularcontainer; guide means for guiding the endless web of film onto thetube; and means for maintaining a tension free slack in the film passingonto the guide means preventing distortion of the profiles.
 11. A form,fill and seal machine for making reclosable zipper bags constructed inaccordance with claim 10:wherein the film is fed over a guide roll andslippage occurs between the guide roll and the film when the web slackexceeds a predetermined amount.
 12. A method for making reclosablezipper bags on a form, fill and seal machine, comprising thesteps:drawing a web of plastic film forwardly over a forming and fillingtube for joining edges of a film having interlocking profiles for atubular container; guiding the film over forming shoulders onto thetube; and maintaining a tension free slack preshaping portion in the webin advance of the forming shoulders for preventing distortion of theprofiles.
 13. A method for making reclosable zipper bags on a form, filland seal machine in accordance with the steps of claim 12:includingwrapping the film over a guiding roller in advance of the formingshoulders; and causing slippage over the guide roll when the web slackbecomes too great.
 14. A method for making reclosable zipper bags on aform, fill and seal machine in accordance with the steps of claim12:including feeding the film over an ascending ramp to the formingshoulders; and positioning a guide roller at the base of the rampfeeding the film at a speed slightly greater than the feed over theforming tube to maintain the slack in the web.
 15. A form, fill and sealmachine for making reclosable zipper bags, comprising in combination:avertical forming and filling tube over which a web of plastic film isshaped having interlocking rib and groove profiles intermediate sideedges of the film; means for joining the edges of the film to form atubular container; forming shoulders at the upper ends of the tube forguiding an endless supply of film onto the tube bringing the film edgestogether over the tube; an inclined ramp leading to the formingshoulders over which the web and profiles are drawn; a feed supplyroller for feeding an endless supply of film to the tube; a guide rollerpositioned at the base of the ramp with the film partially wrappedaround the guide roller, said guide roller frictionally driving the webwhen the web is wrapped at a predetermined minimum tension; and meansdriving the guide roller at a feed speed slightly greater than movementof the film over the tube to cause a tension free web slack on the ramp,the web slipping on the guide roller when the slack increases beyond apredetermined amount and the web wrap over the guide roller falls belowthe minimum tension.
 16. A form, fill and seal machine for makingreclosable zipper bags, comprising in combination:means supplying anendless sheet of film with interlocked rib and groove profilesintermediate side edges of the film; a forming and filling tube overwhich the sheet of plastic film is shaped for joining edges of the filmto form a tubular container; forming shoulders for guiding the sheet offilm onto the tube bringing the film edges together; means feeding thefilm from the supplying means; and means forming a tension-free bubbleloop in the film between the supplying means and the forming shoulders.17. A form, fill and seal machine for making reclosable zipper bagsconstructed in accordance with claim 16:including film proximitydetecting means for detecting the position of the loop.
 18. A form, filland seal machine for making reclosable zipper bags constructed inaccordance with claim 16:including a reciprocating means carrying thefilm forwardly to form the bubble intermediate advancement of the filmover the forming tube.
 19. A form, fill and seal machine for makingreclosable zipper bags constructed in accordance with claim 16:whereinthe loop is formed by a reciprocating roller.
 20. A method for makingreclosable zipper bags on a form, fill and seal machine comprising thesteps:drawing a web of plastic film forwardly over a forming and fillingtube for joining edges of the film to make a tubular container; guidingthe film over forming shoulders onto the tube; and forming atension-free bubble loop in the film in advance of the formingshoulders.
 21. A method of making reclosable zipper bags on a form, filland seal machine in accordance with the steps of claim 20:includingforming the loop intermediate incremental advances of the film over theforming tube.
 22. A method of making reclosable zipper bags on a form,fill and seal machine in accordance with the steps of claim 20:includingsensing the size of the loop and feeding the web forwardly to obtain aloop of a predetermined size.